The present invention relates generally to clamping and positioning devices and, more particularly, to a powered clamp or positioning mechanism having an adjustable stroke.
Powered clamps are commonly used in industrial applications for holding work pieces of many sizes and shapes during forming and machining operations. Such devices include a pneumatically or hydraulically actuated cylinder which causes one or more arms to move through a desired range of rotational motion to push against a work piece. Depending on the specific application, the user may wish to actuate one or two arms which may be vertically or horizontally aligned in an environment contaminated with weld splatter, saw chips, coolants, dust and dirt. Two such conventionally powered clamps are disclosed in U.S. Pat. No. 5,171,001 entitled xe2x80x9cSealed Power Clampxe2x80x9d and U.S. Pat. No. 5,884,903 entitled xe2x80x9cPowered Clamp and Gauging Apparatusxe2x80x9d, both of which are hereby incorporated by reference.
When operating a powered clamp or positioning mechanism, it is often desirable to limit the range of motion of the cylinder within a certain operating window.
Various traditionally powered clamps have been modified to provide a method of adjusting the cylinder stroke of the clamp. The most common device includes a screw threadingly engaged with the rear end cap extending into the piston cylinder. The screw position may be adjusted by rotating the screw thereby adjusting the position of a stop for the piston. Unfortunately, several components must be either moved or temporarily removed to perform the adjustment process. Specifically, the proximity sensors must be moved after each adjustment. In addition, several tools are required to complete these steps. The adjustment screws used within the clamp are very long if a full range of stroke is to be accommodated. An increased length of adjustment screw increases the overall lengths of the cylinder which also increases the likelihood of interference and damage to the adjustment screw and piston. Such elongated cylinders also undesirably require extra space in the end use manufacturing plant. If the adjustment screw is shortened, the stroke is correspondingly shortened thereby increasing the number of cylinder models required to provide a certain stroke range.
In accordance with the teachings of the present invention, a preferred embodiment of an adjustable stroke clamp includes a first piston and a second piston interconnected by a threaded fastener arrangement such that the position of the first piston may be adjusted and maintained relative to the position of the second piston. Accordingly, because the length of a piston cylinder is fixed, the stroke of a piston rod may be adjusted by adjusting the relative distance between the two pistons.
Another aspect of the present invention includes an apparatus to position or clamp a work piece having a body, a generally linearly moving powered actuator positioned in the body, and a mechanism to adjust an available stroke of the actuator. The actuator has a first piston coupled to a second piston. The available stroke is defined by a distance spanned by the first and second pistons.
The adjustable stroke clamp and positioning apparatus of the present invention is highly advantageous over conventional clamps because the present invention includes a floating driver to engage the head of a threaded rod. The piston rod, which is internally threaded in combination with the floating driver, allows stroke adjustment with a single allen wrench. In addition, no disassembly whatsoever is required to adjust the stroke of the clamp. Because clamps are often used in highly contaminated environments, it is highly desirable to be able to adjust the stroke of the cylinder without disassembling it.
Another advantage of the present invention is that the pistons themselves carry probe or sensor pins which cooperate with proximity sensors for indicating the position of the pistons within the cylinder. Unlike other devices presently available, the present invention does not require a repositioning of the sensors after a stroke adjustment. Also, less air is required to actuate the clamp when the pistons are spaced apart. A cost operational savings may be realized based on the reduced volume of compressed fluid required.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.